Disclosure statement

As an adviser to Scottish Labour leader Johann Lamont, Arthur was appointed chair of the party's Welfare Commission, which is putting together a series of proposals for the future of Scotland.

John Curtice and Michael Keating do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.

The people of Scotland are suddenly facing the realistic prospect that monumental change may be in the offing. As most recently confirmed by a shock YouGov poll, support for Yes appears to be rising fast.

We asked our panel what would happen next if Scotland does indeed vote in favour of breaking away from the United Kingdom on September 18.

John Curtice, Professor of Politics, University of Strathclyde/ScotCen Social Research

We must start with what happens at 8am on the Friday morning when the markets open in London. We got a rumble from the markets following YouGov’s poll showing the race tightening. The markets basically have No priced into them. A Yes vote would be a significant shock. Some people are suggesting the UK government should declare a bank holiday on September 19 to avoid any risk of immediate panic – though the pound would still trade overseas.

Meanwhile, all the jigsaw pieces people think are in place for the May 2015 general election would get thrown up in the air. It is unlikely David Cameron would survive until the election. This would be the man who lost the Union. I couldn’t see the Conservatives wanting to fight the election with him as their leader. This might cause a problem for Boris Johnson, who would not yet be in the House of Commons to mount a challenge.

Who would people in England blame? Would they blame the Tories for allowing Scotland to have the referendum, or Labour because they have run much of the No campaign? Would we see the Tories, Labour and Lib Dems arguing with each other about who was responsible? Maybe the principal beneficiaries would be UKIP.

Existing Scottish MPs would have to decide whether to fight the May 2015 general election for what might be less than a 12-month tenure. They would have to consider whether they were going to try to stand for the Scottish parliament in May 2016, though many an existing MSP might not be too keen on that. And if Labour won a UK majority in 2015 thanks to support in Scotland, the government negotiating separation with Scotland on behalf of the rest of the UK would be dependent on Scottish MPs.

North of the border, many politicians and voters on the No side would be devastated. More long term, it is hard to believe that two centre-left parties would continue to dominate. The Conservatives would probably reinvent themselves as a distinct Scottish party of the centre right.

In theory independence negotiations would begin soon after the referendum vote. But the UK government will not be in a position to strike any deals until after May 2015 election. It is not in the UK government’s interests to play negotiations short. It would be in its interests to wait until after the next Scottish election in 2016, in the hope that the SNP no longer had a majority in the Scottish parliament. Of course this assumes that the financial markets were willing to tolerate a long period of negotiation.

Arthur Midwinter, Visiting Professor of Politics, University of Edinburgh

I am worried that relations are now so bad between the SNP and the other side that they can’t recover. I have my doubts that Scottish No campaigners would join independence negotiations. People – Gordon Brown in particular – are very bitter about how Salmond has argued his case. And I am not sure they would want to associate themselves with the economic fall-out.

Market instability would be a factor that both sides would need to consider during negotiations. I could see benefits for both sides in agreeing a deal quickly. But I can’t see a situation in which the UK government would be forced to make any kind of concessions on currency union in the run-up to the 2015 election. That would just undermine their credibility.

I am not sure Cameron would have to go. He has distanced himself from the campaign. In the end his survival will depend more on Tory politics than the referendum.

Cameron is the kind of character that would brazen it out if there was a Yes vote. It is true he wanted only two questions on the ballot, which would have contributed to a defeat if Yes wins, but Labour didn’t want a two-part question either. And there would still have to be a UK election next May. By law they must have it.

Michael Keating, Professor of Politics, University of Aberdeen

There would be shock waves in the rest of the world at what would be a very unusual example of a developed Western country breaking up. There would be huge implications in Spain because the Catalans and the Basques would see that it is possible to secede democratically. There would also be repercussions in Flanders, and people in the north of Italy would get excited but not do very much. Governments all over the world would worry that a political precedent had been set.

The US would want to make sure independence happened as smoothly as possible, and keep Scotland in NATO and the EU. They would have no interest in punishing Scotland. It would be in the interests of the EU member states for a quick settlement that created as little precedent as possible. The smart strategy would be to say it was being done by mutual consent, not unilaterally, and recognised only because the UK is doing so. This would even give the Spanish legal ground to stand on, not that they could avoid setting a precedent.

There would be all kinds of bad feeling on the No side. It would be up to the victorious Yes side to address any resentment, which I think they would do. But if the negotiations became difficult, things could become quite unpleasant.

After a Yes victory, certain things would be sorted out very quickly to reassure the markets, such as currency and debt. There are various possibilities between full currency union and sterlingisation. It would be very much in the Yes side’s interests to avoid doing anything irresponsible, so it might well agree a deal well short of a currency union of equals to maintain use of the pound.

This could involve sterlingisation with a pact on the UK’s terms, including commitments over deficits and debts that would not apply south of the border. The UK government has left itself with enough wriggle room that it could say that its previous refusals to share currency did not include this type of agreement.

I doubt the UK would act vindictively against Scotland. Though opinion in England has hardened over the referendum, it has not gone beyond the point where the UK government could sell a deal to the electorate on the rationale that we are not going to create difficulties that could rebound on us.